A feed mixer apparatus that includes a mixing chamber for receiving feed material, and having a mixing element situated therein for mixing the feed material; a transmission having a plurality of gears and connected with a mixing element; a plurality of mixing chamber sensors positioned to sense at least one of the volume and the level of feed material in the mixing chamber; a control unit having a display and a plurality of user inputs, wherein the control unit is in at least indirect communication with the transmission and the sensors, and wherein the control unit receives a plurality of outputs from one or more of the transmission and sensors, and based at least in part on the plurality of outputs, provides an output command to effectuate a gear change in the transmission.